Brad Stevens and an assistant on his Butler staff showed up for the morning workout at Brownsburg High School to take a look at a player they hoped to reel in.

The players at the Indiana school, located about 15 miles from Butler-based Indianapolis, were completing a drill that involved a chair. They’d dribble up to it, then use a crossover dribble, as if they were trying to shake a defender.

But on one side of the floor, there was a spindly forward who jumped off his right leg and then dunked it with his arm about 11 feet high, a foot above the rim.

The player moved to the other side of the floor, and did the same move while jumping off his left leg.

Stevens, then the head coach at Butler, was stunned.

Players often have one dominant leg that they use for leaping, but to have two?

“I had never seen a guy that — at that time, that we were recruiting, that we had a shot at — do that,” Stevens said.

The player was Gordon Hayward, who eventually signed to play at Butler, where Stevens was the first person to ever tell him that he could play in the NBA.

“We sat down my freshman year, and he said, ‘I think you can play at the next level,’ ” the Utah Jazz forward recalled this summer during the Orlando Summer League.

“It was always a dream of mine, but I didn’t really think that was going to happen. I wasn’t highly recruited. I wasn’t anything big in high school. That’s one thing he showed me, that it’s going to take a lot of work, but that I could get there.”

Hayward starred at Butler, then Utah selected him ninth overall in the 2010 draft. On Wednesday at TD Garden, he’ll face Stevens, now the Celtics coach.

In advance of their matchup, Stevens reminisced about what he saw in Hayward, and his recollection began with the recruitment and that morning workout.

“Here’s a guy that’s got pretty good skill,” Stevens said, reciting his thoughts that day. “He has a great feel for the game. He’s a 9.0 student on a 4.0 scale.”

And he could leap through the roof using whichever of his two legs he pleased.

“So, what’s the missing ingredient?” Stevens said he wondered.

“And the fact was, there wasn’t one. It was just that he grew late.”

Hayward was a stick figure as a high school freshman, standing 5 feet 11 inches, weighing 125 pounds, and he almost gave up basketball.

But he hit a growth spurt, sprouting to 6-6 by his junior season, when Butler started recruiting him. Then, as a senior, he was 6-8.

Once Hayward got to Butler, Stevens said the question then was, “Is he going to have the moxie to be great?”

Then, in their third practice of the year, the Bulldogs were going through late-game situational drills. In one instance, players had nine seconds or less to go the length of the court and score. In another, they had seven seconds to score in the halfcourt. And in another, they had to inbound the ball and try to score with just two seconds left.

“We did four of them in practice,” Stevens said of the drills. “And he made all four of them.”

Stevens walked over to Butler’s director of basketball operations, Kevin Kuwik, who is now an assistant coach at Dayton, and said, “Question, answered.”

Kuwik responded, “A star is born.”

“I’ll never forget that moment,” Stevens said.

Hayward averaged 13.1 points and 6.5 rebounds as a freshman, when he was named the Horizon League Newcomer of the Year and first-team all-conference.

As a sophomore, he averaged 15.5 points and 8.2 rebounds and was named the Horizon League Player of the Year while also helping Butler reach the 2010 national championship game against Duke.

During that tournament run, Hayward hit an impressive, step-back 3-pointer over a Kansas State player in an Elite Eight game. After the shot swished through, Stevens turned to an assistant and said, “He’s gone.”

Sure enough, after the tournament, Hayward declared for the draft and became the first Butler player to reach the NBA in nearly 60 years.

Hayward has averaged 10.5 points through three-plus NBA seasons, and he’s averaging 16.8 points and 6.0 rebounds following a 104-88 loss in Brooklyn on Tuesday, a game in which he scored 22 points in 31 minutes.

Hayward said during the summer that he believes Stevens will have success in the NBA.

More than a few Celtics fans are dreaming of the possibility that Hayward will join Stevens in Boston, especially after the Jazz failed to reach an extension on his rookie deal before the Halloween deadline.

As a result, Hayward will become a restricted free agent at the end of the season and will be able to sign an offer sheet with another team, though the Jazz will have a chance to match that offer.

Deep down, it’s fair to assume that Stevens wouldn’t mind coaching Hayward again, but Stevens can’t say that publicly, lest he run the risk of violating the NBA’s tampering rule, which essentially states that teams can’t publicly discuss their interest in players who are under contract with another team.

Besides that, Stevens said he hadn’t even spoken with Hayward yet this season.

But Wednesday should mark a fun reunion for the coach and former player, who were each stars at Butler and are now both in the NBA.

And, if the stars align, there’s always the chance that Stevens could coach Hayward again — perhaps soon, too.